The present invention provides an apparatus for injecting gas into a vessel. It has particular, but not exclusive application to apparatus for injecting a flow of gas into a metallurgical vessel under high temperature conditions. Such metallurgical vessel may for example be a smelting vessel in which molten metal is produced by a direct smelting process.
A known direct smelting process, which relies on a molten metal layer as a reaction medium, and is generally referred to as the HIsmelt process, is described in International application PCT/AU96/00197 (WO 96/31627) in the name of the applicant.
The HIsmelt process as described in the International application comprises:
(a) forming a bath of molten iron and slag in a vessel;
(b) injecting into the bath:
(i) a metalliferous feed material, typically metal oxides; and
(ii) a solid carbonaceous material, typically coal, which acts as a reductant of the metal oxides and a source of energy; and
(c) smelting metalliferous feed material to metal in the metal layer.
The term xe2x80x9csmeltingxe2x80x9d is herein understood to mean thermal processing wherein chemical reactions that reduce metal oxides take place to produce liquid metal.
The HIsmelt process also comprises post-combusting reaction gases, such as CO and H2 released from the bath in the space above the bath with oxygen-containing gas and transferring the heat generated by the post-combustion to the bath to contribute to the thermal energy required to smelt the metalliferous feed materials.
The HIsmelt process also comprises forming a transition zone above the nominal quiescent surface of the bath in which there is a favourable mass of ascending and thereafter descending droplets or splashes or streams of molten metal and/or slag which provide an effective medium to transfer to the bath the thermal energy generated by post-combusting reaction gases above the bath.
In the HIsmelt process the metalliferous feed material and solid carbonaceous material is injected into the metal layer through a number of lances/tuyeres which are inclined to the vertical so as to extend downwardly and inwardly through the side wall of the smelting vessel and into the lower region of the vessel so as to deliver the solids material into the metal layer in the bottom of the vessel. To promote the post combustion of reaction gases in the upper part of the vessel, a blast of hot air, which may be oxygen enriched, is injected into the upper region of the vessel through the downwardly extending hot air injection lance. To promote effective post combustion of the gases in the upper part of the vessel, it is desirable that the incoming hot air blast exit the lance with a swirling motion. To achieve this, the outlet end of the lance may be fitted with internal flow guides to impart an appropriate swirling motion. The upper regions of the vessel may reach temperatures of the order of 2000xc2x0 C. and the hot air may be delivered into the lance at temperatures of the order of 1100-1400xc2x0 C. The lance must therefore be capable of withstanding extremely high temperatures both internally and on the external walls, particularly at the delivery end of the lance which projects into the combustion zone of the vessel. The present invention provides a lance construction which enables the relevant components to be internally water cooled and to operate in a very high temperature environment.
According to the invention there is provided an apparatus for injecting gas into a vessel, comprising:
a gas flow duct extending from a rear end to a forward end from which to discharge gas from the duct;
an elongate body disposed centrally within the forward end of the duct such that gas flowing through the forward end of the duct will flow over and along the elongate central body;
a plurality of flow directing vanes disposed between the elongate central body and the duct to impart swirl to a gas flow through the forward end of the duct;
cooling water supply and return passage means extending through the wall of the duct from its rear end part to its forward end part for supply and return of cooling water to the forward end part of the duct;
internal cooling water passage means within a duct tip at the forward end of the duct communicating with the cooling water supply and return passage means so as to receive and return a flow of cooling water to internally cool the duct tip; and
cooling water flow passages within the vanes and the elongate central body and communicating with the cooling water supply and return passage means in the forward end part of the duct for flow of water from the supply passage means inwardly through the vanes into the cooling passages of the elongate central body and from those passages outwardly through the vanes to the water return passage means of the duct.
Preferably, the cooling water supply and return passage means comprises first supply and return passages communicating with the internal cooling water passage means in the duct tip and second supply and return passages communicating with the water flow passages in the vanes and central body.
The tip of the duct may be formed as a hollow annular formation projecting forwardly from the remainder of the duct, the hollow formation defining an annular passage constituting said internal cooling water passage means of the duct tip.
The duct may comprise a series of concentric tubes defining a series of annular spaces providing the water flow supply and return passage means. There may be four such tubes defining three concentric annular spaces. The two outermost annular spaces may provide the water supply and return passages for flow of water to and from the internal cooling water passage means of the duct tip. The innermost annular passage may be internally divided so as to provide water supply and return passages for flow of water to and from the cooling water passages in the vanes and elongate central body.
The central body may be generally of cylindrical formation with domed ends.
Preferably, the vanes are shaped to a multi-start helical formation. The vanes may then be connected to the duct at multiple locations spaced circumferentially around the duct. Specifically, there may be four vanes arranged in a four start helical formation and connected to the duct at four locations spaced at 90 degree intervals around the duct at the forward ends of the vanes.
The cooling water supply passage means within the duct may then be comprised of an appropriate number of separated water flow passages each to supply cooling water to one of the vanes. Such separated water flow passages may be formed by dividers within an appropriate annular passage between tubes of the duct extending helically along the duct.
The forward ends of the duct tubes may be connected at their forward ends to the duct tip. The rear ends of the duct tubes may be mounted to allow relative longitudinal movement between them so as to accommodate differential thermal expansion and contraction of the tubes.
The vanes may be connected to the duct and to the central body parts at their forward ends only so as to be free to move along the duct from those connections under thermal expansion.